staging: rtl8712/: Using comparison to true is error prone

clear below issues reported by checkpatch.pl:

CHECK: Using comparison to true is error prone
CHECK: Comparison to NULL should be written "!oldest"

Signed-off-by: John Oldman <john.oldman@polehill.co.uk>
Link: https://lore.kernel.org/r/20200710113113.1648-1-john.oldman@polehill.co.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8712/rtl871x_mlme.c

@@ -264,13 +264,13 @@ struct	wlan_network *r8712_get_oldest_wlan_network(
 	phead = &scanned_queue->queue;
 	plist = phead->next;
 	while (1) {
-		if (end_of_queue_search(phead, plist) ==  true)
+		if (end_of_queue_search(phead, plist))
 			break;
 		pwlan = container_of(plist, struct wlan_network, list);
-		if (pwlan->fixed != true) {
-			if (oldest == NULL ||
+		if (!pwlan->fixed) {
+			if (!oldest ||
 			    time_after((unsigned long)oldest->last_scanned,
-			    (unsigned long)pwlan->last_scanned))
+				       (unsigned long)pwlan->last_scanned))
 				oldest = pwlan;
 		}
 		plist = plist->next;